I had some serious issues about a year ago on Delta when their system screwed up my booking big time
At LHR they fixed it but it was not a brilliant customer experience
The problem re-surfaced at ATL where the lady quickly summoned a supervisor who then summoned someone who appeared to be the Duty Manager. After about 10 minutes of poking around using three terminals they eventually got me on the flight
They couldn't have done more or been pleasanter but the Main Man said it shouldn't have been ABLE to happen - he'd take it up with the software people but that there are so many interconnected sytems these days that they were seeing more and more "impossible" software glitches